U.S. patent number 8,655,400 [Application Number 13/232,547] was granted by the patent office on 2014-02-18 for reduced transmit power for wireless radio coexistence.
This patent grant is currently assigned to Qualcomm Incorporated. The grantee listed for this patent is Pranav Dayal, Xiaoyin He, Tamer Adel Kadous, Ashok Mantravadi, Jibing Wang. Invention is credited to Pranav Dayal, Xiaoyin He, Tamer Adel Kadous, Ashok Mantravadi, Jibing Wang.
United States Patent |
8,655,400 |
Kadous , et al. |
February 18, 2014 |
Reduced transmit power for wireless radio coexistence
Abstract
In user equipments (UEs) with multiple radios, interference
between those radios may be reduced by monitoring radio performance
and adjusting aggressor transmit power levels to ensure victim and
aggressor performance stay within desired operational levels.
Various factors may determine when a reduced power approach is
desired. Such factors may include aggressor transmit power,
received signal strength indicator, victim error rate, throughput
loss, coverage impact, etc. Various methods of reducing transmit
power may be used. For example, for Long Term Evolution
communications, a power headroom report may be altered to adjust a
modulation coding scheme and bandwidth allocated for a particular
UE. For Bluetooth communications a power control mechanism may be
overridden to ensure a device stays within a desired transmit
power. A power reduction loop may be employed to monitor a device's
transmit power.
Inventors: |
Kadous; Tamer Adel (San Diego,
CA), He; Xiaoyin (San Diego, CA), Dayal; Pranav (San
Diego, CA), Mantravadi; Ashok (San Diego, CA), Wang;
Jibing (San Diego, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Kadous; Tamer Adel
He; Xiaoyin
Dayal; Pranav
Mantravadi; Ashok
Wang; Jibing |
San Diego
San Diego
San Diego
San Diego
San Diego |
CA
CA
CA
CA
CA |
US
US
US
US
US |
|
|
Assignee: |
Qualcomm Incorporated (San
Diego, CA)
|
Family
ID: |
44741723 |
Appl.
No.: |
13/232,547 |
Filed: |
September 14, 2011 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20120071106 A1 |
Mar 22, 2012 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61385380 |
Sep 22, 2010 |
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Current U.S.
Class: |
455/522;
455/67.11; 455/127.1; 455/452.1 |
Current CPC
Class: |
H04W
52/16 (20130101); H04W 52/18 (20130101); H04W
52/38 (20130101); H04W 16/14 (20130101) |
Current International
Class: |
H04W
52/00 (20090101); H04B 7/005 (20060101) |
Field of
Search: |
;455/67.11,522,69,63.1,67.13,452.1,452.2,41.2,126,127.1,501,517 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO2010060752 |
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Jun 2010 |
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WO |
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WO2010090567 |
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Aug 2010 |
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WO |
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Other References
"3rd Generation Partnership Project; Technical Specification Group
Radio Access Network; Evolved Universal Terrestrial Radio Access
(E-UTRA) ; Physical layer procedures (Release 9)", 3GPP Standard;
3GPP TS 36.213, 3RD Generation Partnership Project (3GPP), Mobile
Competence Centre ; 650, Route Des Lucioles ; F-06921
Sophia-Antipolis Cedex ; France, No. V9.3.0, Sep. 17, 2010, pp.
1-80, XP050442094, [retrieved on Sep. 17, 2010]. cited by applicant
.
"3rd Generation Partnership Project; Technical Specification Group
Radio Access Network; Evolved Universal Terrestrial Radio Access
(E-UTRA); FDD Home eNode B (HeNB) Radio Frequency (RF) requirements
analysis (Release 9)" 3GPP Standard; 3GPP TR 36.921, 3rd Generation
Partnership Project (3GPP), Mobile Competence Centre ; 650, Route
Des Lucioles ; F-06921 Sophia-Antipolis Cedex ; France, No. V9.0.0,
Apr. 6, 2010, pp. 1-46, XP050402484, [retrieved on Apr. 6, 2010].
cited by applicant .
International Search Report and Written
Opinion--PCT/US2011/052813--ISA/EPO--Nov. 23, 2011. cited by
applicant .
"Types of TDM Solutions for LTE ISM Coexistence," 3GPP TSG-RAN WG2
Meeting #71-BIS, R2-105764, Oct. 11-15, 2010, 7 pages. cited by
applicant.
|
Primary Examiner: Lee; John J
Attorney, Agent or Firm: Seyfarth Shaw LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit of U.S. Provisional Patent
Application No. 61/385,380 entitled "REDUCED TRANSMIT POWER FOR
WIRELESS RADIO COEXISTENCE," filed Sep. 22, 2010, the disclosure of
which is expressly incorporated herein by reference in its
entirety.
Claims
What is claimed is:
1. A method for wireless communication, comprising: determining a
performance metric of an aggressor radio and a performance metric
of a victim radio; and dynamically setting a non-zero maximum
transmit power of the aggressor radio based on at least one of the
performance metric of the victim radio and the performance metric
of the aggressor radio in order to meet target performance criteria
for the victim radio and aggressor radio.
2. The method of claim 1 further comprising adjusting the target
performance criteria based on a relative priority of communications
of the victim and aggressor radios.
3. The method of claim 1 further comprising adjusting the target
performance criteria based on communication conditions of at least
one of the victim and aggressor radios.
4. The method of claim 1, further comprising setting a lowest
amount of maximum aggressor transmit power to meet a threshold
defined by a maximum performance loss of the aggressor radio.
5. The method of claim 1, further comprising sending a report of a
gap between a current aggressor transmit power and a maximum
aggressor transmit power used for power and rate control, based on
the maximum aggressor transmit power.
6. The method of claim 1, in which the performance metric of the
victim radio comprises at least one of a level of interference
observed at the victim radio, a throughput loss observed at the
victim radio, an error rate observed at the victim radio, and a
received signal strength indicator (RSSI) observed at the victim
radio.
7. The method of claim 1, in which the performance metric of the
aggressor radio comprises at least one of aggressor throughput, an
error rate observed at the aggressor radio, and a delay observed at
the aggressor radio.
8. The method of claim 1, further comprising: resetting the maximum
transmit power to ignore the performance metric of the victim radio
when observing unacceptable performance at the aggressor radio
while the maximum transmit power is at a lowest amount of maximum
power to meet a performance threshold; and invoking an alternative
coexistence solution.
9. The method of claim 1, further comprising: resetting the maximum
transmit power to ignore the performance metric of the victim radio
when the aggressor radio needs additional power due to a coverage
issue; and invoking an alternative coexistence solution.
10. The method of claim 1, in which the aggressor radio comprises
one of a long term evolution (LTE) radio, Bluetooth radio, and
wireless local area network (WLAN) radio.
11. An apparatus for wireless communications, comprising: means for
determining a performance metric of an aggressor radio and a
performance metric of a victim radio; and means for dynamically
setting a non-zero maximum transmit power of the aggressor radio
based on at least one of the performance metric of the victim radio
and the performance metric of the aggressor radio in order to meet
target performance criteria for the victim radio and aggressor
radio.
12. A computer program product configured for wireless
communication, the computer program product comprising: a
non-transitory computer-readable medium having non-transitory
program code recorded thereon, the non-transitory program code
comprising: program code to determine a performance metric of an
aggressor radio and a performance metric of a victim radio; and
program code to dynamically set a non-zero maximum transmit power
of the aggressor radio based on at least one of the performance
metric of the victim radio and the performance metric of the
aggressor radio in order to meet target performance criteria for
the victim radio and aggressor radio.
13. An apparatus configured for wireless communication, the
apparatus comprising: a memory; and at least one processor coupled
to the memory, the at least one processor being configured: to
determine a performance metric of an aggressor radio and a
performance metric of a victim radio; and to dynamically set a
non-zero maximum transmit power of the aggressor radio based on at
least one of the performance metric of the victim radio and the
performance metric of the aggressor radio in order to meet target
performance criteria for the victim radio and aggressor radio.
14. The apparatus of claim 13 in which the at least one processor
is further configured to adjust the target performance criteria
based on a relative priority of communications of the victim and
aggressor radios.
15. The apparatus of claim 13 in which the at least one processor
is further configured to adjust the target performance criteria
based on communication conditions of at least one of the victim and
aggressor radios.
16. The apparatus of claim 13, in which the at least one processor
is further configured to set a lowest amount of maximum aggressor
transmit power to meet a threshold defined by a maximum performance
loss of the aggressor radio.
17. The apparatus of claim 13, in which the at least one processor
is further configured to send a report of a gap between a current
aggressor transmit power and a maximum aggressor transmit power
used for power and rate control, based on the maximum aggressor
transmit power.
18. The apparatus of claim 13, in which the performance metric of
the victim radio comprises at least one of a level of interference
observed at the victim radio, a throughput loss observed at the
victim radio, an error rate observed at the victim radio, and a
received signal strength indicator (RSSI) observed at the victim
radio.
19. The apparatus of claim 13, in which the performance metric of
the aggressor radio comprises at least one of aggressor throughput,
an error rate observed at the aggressor radio, and a delay observed
at the aggressor radio.
20. The apparatus of claim 13, in which the at least one processor
is further configured: to reset the maximum transmit power to
ignore the performance metric of the victim radio when observing
unacceptable performance at the aggressor radio while the maximum
transmit power is at a lowest amount of maximum power to meet a
performance threshold; and to invoke an alternative coexistence
solution.
21. The apparatus of claim 13, in which the at least one processor
is further configured: to reset the maximum transmit power to
ignore the performance metric of the victim radio when the
aggressor radio needs additional power due to a coverage issue; and
to invoke an alternative coexistence solution.
22. The apparatus of claim 13, in which the aggressor radio
comprises one of a long term evolution (LTE) radio, Bluetooth
radio, and wireless local area network (WLAN) radio.
Description
TECHNICAL FIELD
The present description is related, generally, to multi-radio
techniques and, more specifically, to coexistence techniques for
multi-radio devices.
BACKGROUND
Wireless communication systems are widely deployed to provide
various types of communication content such as voice, data, and so
on. These systems may be multiple-access systems capable of
supporting communication with multiple users by sharing the
available system resources (e.g., bandwidth and transmit power).
Examples of such multiple access systems include code division
multiple access (CDMA) systems, time division multiple access
(TDMA) systems, frequency division multiple access (FDMA) systems,
3GPP Long Term Evolution (LTE) systems, and orthogonal frequency
division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can
simultaneously support communication for multiple wireless
terminals. Each terminal communicates with one or more base
stations via transmissions on the forward and reverse links. The
forward link (or downlink) refers to the communication link from
the base stations to the terminals, and the reverse link (or
uplink) refers to the communication link from the terminals to the
base stations. This communication link may be established via a
single-in-single-out, multiple-in-single-out or a
multiple-in-multiple out (MIMO) system.
Some conventional advanced devices include multiple radios for
transmitting/receiving using different Radio Access Technologies
(RATs). Examples of RATs include, e.g., Universal Mobile
Telecommunications System (UMTS), Global System for Mobile
Communications (GSM), cdma2000, WiMAX, WLAN (e.g., WiFi),
Bluetooth, LTE, and the like.
An example mobile device includes an LTE User Equipment (UE), such
as a fourth generation (4G) mobile phone. Such 4G phone may include
various radios to provide a variety of functions for the user. For
purposes of this example, the 4G phone includes an LTE radio for
voice and data, an IEEE 802.11 (WiFi) radio, a Global Positioning
System (GPS) radio, and a Bluetooth radio, where two of the above
or all four may operate simultaneously. While the different radios
provide useful functionalities for the phone, their inclusion in a
single device gives rise to coexistence issues. Specifically,
operation of one radio may in some cases interfere with operation
of another radio through radiative, conductive, resource collision,
and/or other interference mechanisms. Coexistence issues include
such interference.
This is especially true for the LTE uplink channel, which is
adjacent to the Industrial Scientific and Medical (ISM) band and
may cause interference therewith. It is noted that Bluetooth and
some Wireless LAN (WLAN) channels fall within the ISM band. In some
instances, a Bluetooth error rate can become unacceptable when LTE
is active in some channels of Band 7 or even Band 40 for some
Bluetooth channel conditions. Even though there is no significant
degradation to LTE, simultaneous operation with Bluetooth can
result in disruption in voice services terminating in a Bluetooth
headset. Such disruption may be unacceptable to the consumer. A
similar issue exists when LTE transmissions interfere with GPS.
Currently, there is no mechanism that can solve this issue since
LTE by itself does not experience any degradation
With reference specifically to LTE, it is noted that a UE
communicates with an evolved NodeB (eNB; e.g., a base station for a
wireless communications network) to inform the eNB of interference
seen by the UE on the downlink. Furthermore, the eNB may be able to
estimate interference at the UE using a downlink error rate. In
some instances, the eNB and the UE can cooperate to find a solution
that reduces interference at the UE, even interference due to
radios within the UE itself. However, in conventional LTE, the
interference estimates regarding the downlink may not be adequate
to comprehensively address interference.
In one instance, an LTE uplink signal interferes with a Bluetooth
signal or WLAN signal. However, such interference is not reflected
in the downlink measurement reports at the eNB. As a result,
unilateral action on the part of the UE (e.g., moving the uplink
signal to a different channel) may be thwarted by the eNB, which is
not aware of the uplink coexistence issue and seeks to undo the
unilateral action. For instance, even if the UE re-establishes the
connection on a different frequency channel, the network can still
handover the UE back to the original frequency channel that was
corrupted by the in-device interference. This is a likely scenario
because the desired signal strength on the corrupted channel may
sometimes be higher than reflected in the measurement reports of
the new channel based on Reference Signal Received Power (RSRP) to
the eNB. Hence, a ping-pong effect of being transferred back and
forth between the corrupted channel and the desired channel can
happen if the eNB uses RSRP reports to make handover decisions.
Other unilateral action on the part of the UE, such as simply
stopping uplink communications without coordination of the eNB may
cause power loop malfunctions at the eNB. Additional issues that
exist in conventional LTE include a general lack of ability on the
part of the UE to suggest desired configurations as an alternative
to configurations that have coexistence issues. For at least these
reasons, uplink coexistence issues at the UE may remain unresolved
for a long time period, degrading performance and efficiency for
other radios of the UE.
SUMMARY
Offered is a method of wireless communication. The method includes
determining a performance metric of an aggressor radio and a
performance metric of a victim radio. The method also includes
dynamically setting a maximum transmit power of the aggressor radio
based on at least one of the performance metric of the victim radio
and the performance metric of the aggressor radio. The maximum
transmit power of the aggressor radio is set in order to meet
target performance criteria for the victim radio and aggressor
radio.
Offered is an apparatus for wireless communication. The apparatus
includes means for determining a performance metric of an aggressor
radio and a performance metric of a victim radio. The apparatus
also includes means for dynamically setting a maximum transmit
power of the aggressor radio based on at least one of the
performance metric of the victim radio and the performance metric
of the aggressor radio. The maximum transmit power of the aggressor
radio is set in order to meet target performance criteria for the
victim radio and aggressor radio.
Offered is a computer program product configured for wireless
communication. The computer program product includes a
non-transitory computer-readable medium having non-transitory
program code recorded thereon. The non-transitory program code
includes program code to determine a performance metric of an
aggressor radio and a performance metric of a victim radio. The
non-transitory program code also includes program code to
dynamically set a maximum transmit power of the aggressor radio
based on at least one of the performance metric of the victim radio
and the performance metric of the aggressor radio. The maximum
transmit power of the aggressor radio is set in order to meet
target performance criteria for the victim radio and aggressor
radio.
Offered is an apparatus for wireless communication. The apparatus
includes a memory and a processor(s) coupled to the memory. The
processor(s) is configured to determine a performance metric of an
aggressor radio and a performance metric of a victim radio. The
processor(s) is also configured to dynamically set a maximum
transmit power of the aggressor radio based on at least one of the
performance metric of the victim radio and the performance metric
of the aggressor radio. The maximum transmit power of the aggressor
radio is set in order to meet target performance criteria for the
victim radio and aggressor radio.
Additional features and advantages of the disclosure will be
described below. It should be appreciated by those skilled in the
art that this disclosure may be readily utilized as a basis for
modifying or designing other structures for carrying out the same
purposes of the present disclosure. It should also be realized by
those skilled in the art that such equivalent constructions do not
depart from the teachings of the disclosure as set forth in the
appended claims. The novel features, which are believed to be
characteristic of the disclosure, both as to its organization and
method of operation, together with further objects and advantages,
will be better understood from the following description when
considered in connection with the accompanying figures. It is to be
expressly understood, however, that each of the figures is provided
for the purpose of illustration and description only and is not
intended as a definition of the limits of the present
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The features, nature, and advantages of the present disclosure will
become more apparent from the detailed description set forth below
when taken in conjunction with the drawings in which like reference
characters identify correspondingly throughout.
FIG. 1 illustrates a multiple access wireless communication system
according to one aspect.
FIG. 2 is a block diagram of a communication system according to
one aspect.
FIG. 3 illustrates an exemplary frame structure in downlink Long
Term Evolution (LTE) communications.
FIG. 4 is a block diagram conceptually illustrating an exemplary
frame structure in uplink Long Term Evolution (LTE)
communications.
FIG. 5 illustrates an example wireless communication
environment.
FIG. 6 is a block diagram of an example design for a multi-radio
wireless device.
FIG. 7 is graph showing respective potential collisions between
seven example radios in a given decision period.
FIG. 8 is a diagram showing operation of an example Coexistence
Manager (C.times.M) over time.
FIG. 9 is a block diagram illustrating adjacent frequency
bands.
FIG. 10 is a block diagram of a system for providing support within
a wireless communication environment for multi-radio coexistence
management according to one aspect of the present disclosure.
FIG. 11 is a block diagram illustrating reducing transmit power for
multiple radio coexistence according to one aspect of the present
disclosure.
FIG. 12 is a block diagram illustrating components for reducing
transmit power for multiple radio coexistence according to one
aspect of the present disclosure.
DETAILED DESCRIPTION
Various aspects of the disclosure provide techniques to mitigate
coexistence issues in multi-radio devices, where significant
in-device coexistence problems can exist between, e.g., the LTE and
Industrial Scientific and Medical (ISM) bands (e.g., for BT/WLAN).
As explained above, some coexistence issues persist because an eNB
is not aware of interference on the UE side that is experienced by
other radios. According to one aspect, the UE declares a Radio Link
Failure (RLF) and autonomously accesses a new channel or Radio
Access Technology (RAT) if there is a coexistence issue on the
present channel. The UE can declare a RLF in some examples for the
following reasons: 1) UE reception is affected by interference due
to coexistence, and 2) the UE transmitter is causing disruptive
interference to another radio. The UE then sends a message
indicating the coexistence issue to the eNB while reestablishing
connection in the new channel or RAT. The eNB becomes aware of the
coexistence issue by virtue of having received the message.
The techniques described herein can be used for various wireless
communication networks such as Code Division Multiple Access (CDMA)
networks, Time Division Multiple Access (TDMA) networks, Frequency
Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA)
networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms
"networks" and "systems" are often used interchangeably. A CDMA
network can implement a radio technology such as Universal
Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes
Wideband-CDMA (W-CDMA) and Low Chip Rate (LCR). cdma2000 covers
IS-2000, IS-95 and IS-856 standards. A TDMA network can implement a
radio technology such as Global System for Mobile Communications
(GSM). An OFDMA network can implement a radio technology such as
Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20,
Flash-OFDM.RTM., etc. UTRA, E-UTRA, and GSM are part of Universal
Mobile Telecommunication System (UMTS). Long Term Evolution (LTE)
is an upcoming release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM,
UMTS and LTE are described in documents from an organization named
"3.sup.rd Generation Partnership Project" (3GPP). CDMA2000 is
described in documents from an organization named "3.sup.rd
Generation Partnership Project 2" (3GPP2). These various radio
technologies and standards are known in the art. For clarity,
certain aspects of the techniques are described below for LTE, and
LTE terminology is used in portions of the description below.
Single carrier frequency division multiple access (SC-FDMA), which
utilizes single carrier modulation and frequency domain
equalization is a technique that can be utilized with various
aspects described herein. SC-FDMA has similar performance and
essentially the same overall complexity as those of an OFDMA
system. SC-FDMA signal has lower peak-to-average power ratio (PAPR)
because of its inherent single carrier structure. SC-FDMA has drawn
great attention, especially in the uplink communications where
lower PAPR greatly benefits the mobile terminal in terms of
transmit power efficiency. It is currently a working assumption for
an uplink multiple access scheme in 3GPP Long Term Evolution (LTE),
or Evolved UTRA.
Referring to FIG. 1, a multiple access wireless communication
system according to one aspect is illustrated. An evolved Node B
100 (eNB) includes a computer 115 that has processing resources and
memory resources to manage the LTE communications by allocating
resources and parameters, granting/denying requests from user
equipment, and/or the like. The eNB 100 also has multiple antenna
groups, one group including antenna 104 and antenna 106, another
group including antenna 108 and antenna 110, and an additional
group including antenna 112 and antenna 114. In FIG. 1, only two
antennas are shown for each antenna group, however, more or fewer
antennas can be utilized for each antenna group. A User Equipment
(UE) 116 (also referred to as an Access Terminal (AT)) is in
communication with antennas 112 and 114, while antennas 112 and 114
transmit information to the UE 116 over an uplink (UL) 188. The UE
122 is in communication with antennas 106 and 108, while antennas
106 and 108 transmit information to the UE 122 over a downlink (DL)
126 and receive information from the UE 122 over an uplink 124. In
a frequency division duplex (FDD) system, communication links 118,
120, 124 and 126 can use different frequencies for communication.
For example, the downlink 120 can use a different frequency than
used by the uplink 118.
Each group of antennas and/or the area in which they are designed
to communicate is often referred to as a sector of the eNB. In this
aspect, respective antenna groups are designed to communicate to
UEs in a sector of the areas covered by the eNB 100.
In communication over the downlinks 120 and 126, the transmitting
antennas of the eNB 100 utilize beamforming to improve the
signal-to-noise ratio of the uplinks for the different UEs 116 and
122. Also, an eNB using beamforming to transmit to UEs scattered
randomly through its coverage causes less interference to UEs in
neighboring cells than a UE transmitting through a single antenna
to all its UEs.
An eNB can be a fixed station used for communicating with the
terminals and can also be referred to as an access point, base
station, or some other terminology. A UE can also be called an
access terminal, a wireless communication device, terminal, or some
other terminology.
FIG. 2 is a block diagram of an aspect of a transmitter system 210
(also known as an eNB) and a receiver system 250 (also known as a
UE) in a MIMO system 200. In some instances, both a UE and an eNB
each have a transceiver that includes a transmitter system and a
receiver system. At the transmitter system 210, traffic data for a
number of data streams is provided from a data source 212 to a
transmit (TX) data processor 214.
A MIMO system employs multiple (N.sub.T) transmit antennas and
multiple (N.sub.R) receive antennas for data transmission. A MIMO
channel formed by the N.sub.T transmit and N.sub.R receive antennas
may be decomposed into N.sub.S independent channels, which are also
referred to as spatial channels, wherein N.sub.S.ltoreq.min
{N.sub.T, N.sub.R}. Each of the N.sub.S independent channels
corresponds to a dimension. The MIMO system can provide improved
performance (e.g., higher throughput and/or greater reliability) if
the additional dimensionalities created by the multiple transmit
and receive antennas are utilized.
A MIMO system supports time division duplex (TDD) and frequency
division duplex (FDD) systems. In a TDD system, the uplink and
downlink transmissions are on the same frequency region so that the
reciprocity principle allows the estimation of the downlink channel
from the uplink channel. This enables the eNB to extract transmit
beamforming gain on the downlink when multiple antennas are
available at the eNB.
In an aspect, each data stream is transmitted over a respective
transmit antenna. The TX data processor 214 formats, codes, and
interleaves the traffic data for each data stream based on a
particular coding scheme selected for that data stream to provide
coded data.
The coded data for each data stream can be multiplexed with pilot
data using OFDM techniques. The pilot data is a known data pattern
processed in a known manner and can be used at the receiver system
to estimate the channel response. The multiplexed pilot and coded
data for each data stream is then modulated (e.g., symbol mapped)
based on a particular modulation scheme (e.g., BPSK, QSPK, M-PSK,
or M-QAM) selected for that data stream to provide modulation
symbols. The data rate, coding, and modulation for each data stream
can be determined by instructions performed by a processor 230
operating with a memory 232.
The modulation symbols for respective data streams are then
provided to a TX MIMO processor 220, which can further process the
modulation symbols (e.g., for OFDM). The TX MIMO processor 220 then
provides N.sub.T modulation symbol streams to N.sub.T transmitters
(TMTR) 222a through 222t. In certain aspects, the TX MIMO processor
220 applies beamforming weights to the symbols of the data streams
and to the antenna from which the symbol is being transmitted.
Each transmitter 222 receives and processes a respective symbol
stream to provide one or more analog signals, and further
conditions (e.g., amplifies, filters, and upconverts) the analog
signals to provide a modulated signal suitable for transmission
over the MIMO channel. N.sub.T modulated signals from the
transmitters 222a through 222t are then transmitted from N.sub.T
antennas 224a through 224t, respectively.
At a receiver system 250, the transmitted modulated signals are
received by N.sub.R antennas 252a through 252r and the received
signal from each antenna 252 is provided to a respective receiver
(RCVR) 254a through 254r. Each receiver 254 conditions (e.g.,
filters, amplifies, and downconverts) a respective received signal,
digitizes the conditioned signal to provide samples, and further
processes the samples to provide a corresponding "received" symbol
stream.
An RX data processor 260 then receives and processes the N.sub.R
received symbol streams from N.sub.R receivers 254 based on a
particular receiver processing technique to provide N.sub.R
"detected" symbol streams. The RX data processor 260 then
demodulates, deinterleaves, and decodes each detected symbol stream
to recover the traffic data for the data stream. The processing by
the RX data processor 260 is complementary to the processing
performed by the TX MIMO processor 220 and the TX data processor
214 at the transmitter system 210.
A processor 270 (operating with a memory 272) periodically
determines which pre-coding matrix to use (discussed below). The
processor 270 formulates an uplink message having a matrix index
portion and a rank value portion.
The uplink message can include various types of information
regarding the communication link and/or the received data stream.
The uplink message is then processed by a TX data processor 238,
which also receives traffic data for a number of data streams from
a data source 236, modulated by a modulator 280, conditioned by
transmitters 254a through 254r, and transmitted back to the
transmitter system 210.
At the transmitter system 210, the modulated signals from the
receiver system 250 are received by antennas 224, conditioned by
receivers 222, demodulated by a demodulator 240, and processed by
an RX data processor 242 to extract the uplink message transmitted
by the receiver system 250. The processor 230 then determines which
pre-coding matrix to use for determining the beamforming weights,
then processes the extracted message.
FIG. 3 is a block diagram conceptually illustrating an exemplary
frame structure in downlink Long Term Evolution (LTE)
communications. The transmission timeline for the downlink may be
partitioned into units of radio frames. Each radio frame may have a
predetermined duration (e.g., 10 milliseconds (ms)) and may be
partitioned into 10 subframes with indices of 0 through 9. Each
subframe may include two slots. Each radio frame may thus include
20 slots with indices of 0 through 19. Each slot may include L
symbol periods, e.g., 7 symbol periods for a normal cyclic prefix
(as shown in FIG. 3) or 6 symbol periods for an extended cyclic
prefix. The 2L symbol periods in each subframe may be assigned
indices of 0 through 2L-1. The available time frequency resources
may be partitioned into resource blocks. Each resource block may
cover N subcarriers (e.g., 12 subcarriers) in one slot.
In LTE, an eNB may send a Primary Synchronization Signal (PSS) and
a Secondary Synchronization Signal (SSS) for each cell in the eNB.
The PSS and SSS may be sent in symbol periods 6 and 5,
respectively, in each of subframes 0 and 5 of each radio frame with
the normal cyclic prefix, as shown in FIG. 3. The synchronization
signals may be used by UEs for cell detection and acquisition. The
eNB may send a Physical Broadcast Channel (PBCH) in symbol periods
0 to 3 in slot 1 of subframe 0. The PBCH may carry certain system
information.
The eNB may send a Cell-specific Reference Signal (CRS) for each
cell in the eNB. The CRS may be sent in symbols 0, 1, and 4 of each
slot in case of the normal cyclic prefix, and in symbols 0, 1, and
3 of each slot in case of the extended cyclic prefix. The CRS may
be used by UEs for coherent demodulation of physical channels,
timing and frequency tracking, Radio Link Monitoring (RLM),
Reference Signal Received Power (RSRP), and Reference Signal
Received Quality (RSRQ) measurements, etc.
The eNB may send a Physical Control Format Indicator Channel
(PCFICH) in the first symbol period of each subframe, as seen in
FIG. 3. The PCFICH may convey the number of symbol periods (M) used
for control channels, where M may be equal to 1, 2 or 3 and may
change from subframe to subframe. M may also be equal to 4 for a
small system bandwidth, e.g., with less than 10 resource blocks. In
the example shown in FIG. 3, M=3. The eNB may send a Physical HARQ
Indicator Channel (PHICH) and a Physical Downlink Control Channel
(PDCCH) in the first M symbol periods of each subframe. The PDCCH
and PHICH are also included in the first three symbol periods in
the example shown in FIG. 3. The PHICH may carry information to
support Hybrid Automatic Repeat Request (HARQ). The PDCCH may carry
information on resource allocation for UEs and control information
for downlink channels. The eNB may send a Physical Downlink Shared
Channel (PDSCH) in the remaining symbol periods of each subframe.
The PDSCH may carry data for UEs scheduled for data transmission on
the downlink. The various signals and channels in LTE are described
in 3GPP TS 36.211, entitled "Evolved Universal Terrestrial Radio
Access (E-UTRA); Physical Channels and Modulation," which is
publicly available.
The eNB may send the PSS, SSS and PBCH in the center 1.08 MHz of
the system bandwidth used by the eNB. The eNB may send the PCFICH
and PHICH across the entire system bandwidth in each symbol period
in which these channels are sent. The eNB may send the PDCCH to
groups of UEs in certain portions of the system bandwidth. The eNB
may send the PDSCH to specific UEs in specific portions of the
system bandwidth. The eNB may send the PSS, SSS, PBCH, PCFICH and
PHICH in a broadcast manner to all UEs, may send the PDCCH in a
unicast manner to specific UEs, and may also send the PDSCH in a
unicast manner to specific UEs.
A number of resource elements may be available in each symbol
period. Each resource element may cover one subcarrier in one
symbol period and may be used to send one modulation symbol, which
may be a real or complex value. Resource elements not used for a
reference signal in each symbol period may be arranged into
resource element groups (REGs). Each REG may include four resource
elements in one symbol period. The PCFICH may occupy four REGs,
which may be spaced approximately equally across frequency, in
symbol period 0. The PHICH may occupy three REGs, which may be
spread across frequency, in one or more configurable symbol
periods. For example, the three REGs for the PHICH may all belong
in symbol period 0 or may be spread in symbol periods 0, 1 and 2.
The PDCCH may occupy 9, 18, 32 or 64 REGs, which may be selected
from the available REGs, in the first M symbol periods. Only
certain combinations of REGs may be allowed for the PDCCH.
A UE may know the specific REGs used for the PHICH and the PCFICH.
The UE may search different combinations of REGs for the PDCCH. The
number of combinations to search is typically less than the number
of allowed combinations for the PDCCH. An eNB may send the PDCCH to
the UE in any of the combinations that the UE will search.
FIG. 4 is a block diagram conceptually illustrating an exemplary
frame structure in uplink Long Term Evolution (LTE) communications.
The available Resource Blocks (RBs) for the uplink may be
partitioned into a data section and a control section. The control
section may be formed at the two edges of the system bandwidth and
may have a configurable size. The resource blocks in the control
section may be assigned to UEs for transmission of control
information. The data section may include all resource blocks not
included in the control section. The design in FIG. 4 results in
the data section including contiguous subcarriers, which may allow
a single UE to be assigned all of the contiguous subcarriers in the
data section.
A UE may be assigned resource blocks in the control section to
transmit control information to an eNB. The UE may also be assigned
resource blocks in the data section to transmit data to the eNodeB.
The UE may transmit control information in a Physical Uplink
Control Channel (PUCCH) on the assigned resource blocks in the
control section. The UE may transmit only data or both data and
control information in a Physical Uplink Shared Channel (PUSCH) on
the assigned resource blocks in the data section. An uplink
transmission may span both slots of a subframe and may hop across
frequency as shown in FIG. 4.
The PSS, SSS, CRS, PBCH, PUCCH and PUSCH in LTE are described in
3GPP TS 36.211, entitled "Evolved Universal Terrestrial Radio
Access (E-UTRA); Physical Channels and Modulation," which is
publicly available.
In an aspect, described herein are systems and methods for
providing support within a wireless communication environment, such
as a 3GPP LTE environment or the like, to facilitate multi-radio
coexistence solutions.
Referring now to FIG. 5, illustrated is an example wireless
communication environment 500 in which various aspects described
herein can function. The wireless communication environment 500 can
include a wireless device 510, which can be capable of
communicating with multiple communication systems. These systems
can include, for example, one or more cellular systems 520 and/or
530, one or more WLAN systems 540 and/or 550, one or more wireless
personal area network (WPAN) systems 560, one or more broadcast
systems 570, one or more satellite positioning systems 580, other
systems not shown in FIG. 5, or any combination thereof. It should
be appreciated that in the following description the terms
"network" and "system" are often used interchangeably.
The cellular systems 520 and 530 can each be a CDMA, TDMA, FDMA,
OFDMA, Single Carrier FDMA (SC-FDMA), or other suitable system. A
CDMA system can implement a radio technology such as Universal
Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes
Wideband CDMA (WCDMA) and other variants of CDMA. Moreover,
cdma2000 covers IS-2000 (CDMA2000 1X), IS-95 and IS-856 (HRPD)
standards. A TDMA system can implement a radio technology such as
Global System for Mobile Communications (GSM), Digital Advanced
Mobile Phone System (D-AMPS), etc. An OFDMA system can implement a
radio technology such as Evolved UTRA (E-UTRA), Ultra Mobile
Broadband (UMB), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM.RTM.,
etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication
System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced
(LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA,
UMTS, LTE, LTE-A and GSM are described in documents from an
organization named "3.sup.rd Generation Partnership Project"
(3GPP). cdma2000 and UMB are described in documents from an
organization named "3.sup.rd Generation Partnership Project 2"
(3GPP2). In an aspect, the cellular system 520 can include a number
of base stations 522, which can support bi-directional
communication for wireless devices within their coverage.
Similarly, the cellular system 530 can include a number of base
stations 532 that can support bi-directional communication for
wireless devices within their coverage.
WLAN systems 540 and 550 can respectively implement radio
technologies such as IEEE 802.11 (WiFi), Hiperlan, etc. The WLAN
system 540 can include one or more access points 542 that can
support bi-directional communication. Similarly, the WLAN system
550 can include one or more access points 552 that can support
bi-directional communication. The WPAN system 560 can implement a
radio technology such as Bluetooth (BT), IEEE 802.15, etc. Further,
the WPAN system 560 can support bi-directional communication for
various devices such as wireless device 510, a headset 562, a
computer 564, a mouse 566, or the like.
The broadcast system 570 can be a television (TV) broadcast system,
a frequency modulation (FM) broadcast system, a digital broadcast
system, etc. A digital broadcast system can implement a radio
technology such as MediaFLO.TM., Digital Video Broadcasting for
Handhelds (DVB-H), Integrated Services Digital Broadcasting for
Terrestrial Television Broadcasting (ISDB-T), or the like. Further,
the broadcast system 570 can include one or more broadcast stations
572 that can support one-way communication.
The satellite positioning system 580 can be the United States
Global Positioning System (GPS), the European Galileo system, the
Russian GLONASS system, the Quasi-Zenith Satellite System (QZSS)
over Japan, the Indian Regional Navigational Satellite System
(IRNSS) over India, the Beidou system over China, and/or any other
suitable system. Further, the satellite positioning system 580 can
include a number of satellites 582 that transmit signals for
position determination.
In an aspect, the wireless device 510 can be stationary or mobile
and can also be referred to as a user equipment (UE), a mobile
station, a mobile equipment, a terminal, an access terminal, a
subscriber unit, a station, etc. The wireless device 510 can be
cellular phone, a personal digital assistance (PDA), a wireless
modem, a handheld device, a laptop computer, a cordless phone, a
wireless local loop (WLL) station, etc. In addition, a wireless
device 510 can engage in two-way communication with the cellular
system 520 and/or 530, the WLAN system 540 and/or 550, devices with
the WPAN system 560, and/or any other suitable systems(s) and/or
devices(s). The wireless device 510 can additionally or
alternatively receive signals from the broadcast system 570 and/or
satellite positioning system 580. In general, it can be appreciated
that the wireless device 510 can communicate with any number of
systems at any given moment. Also, the wireless device 510 may
experience coexistence issues among various ones of its constituent
radio devices that operate at the same time. Accordingly, device
510 includes a coexistence manager (C.times.M, not shown) that has
a functional module to detect and mitigate coexistence issues, as
explained further below.
Turning next to FIG. 6, a block diagram is provided that
illustrates an example design for a multi-radio wireless device 600
and may be used as an implementation of the radio 510 of FIG. 5. As
FIG. 6 illustrates, the wireless device 600 can include N radios
620a through 620n, which can be coupled to N antennas 610a through
610n, respectively, where N can be any integer value. It should be
appreciated, however, that respective radios 620 can be coupled to
any number of antennas 610 and that multiple radios 620 can also
share a given antenna 610.
In general, a radio 620 can be a unit that radiates or emits energy
in an electromagnetic spectrum, receives energy in an
electromagnetic spectrum, or generates energy that propagates via
conductive means. By way of example, a radio 620 can be a unit that
transmits a signal to a system or a device or a unit that receives
signals from a system or device. Accordingly, it can be appreciated
that a radio 620 can be utilized to support wireless communication.
In another example, a radio 620 can also be a unit (e.g., a screen
on a computer, a circuit board, etc.) that emits noise, which can
impact the performance of other radios. Accordingly, it can be
further appreciated that a radio 620 can also be a unit that emits
noise and interference without supporting wireless
communication.
In an aspect, respective radios 620 can support communication with
one or more systems. Multiple radios 620 can additionally or
alternatively be used for a given system, e.g., to transmit or
receive on different frequency bands (e.g., cellular and PCS
bands).
In another aspect, a digital processor 630 can be coupled to radios
620a through 620n and can perform various functions, such as
processing for data being transmitted or received via the radios
620. The processing for each radio 620 can be dependent on the
radio technology supported by that radio and can include
encryption, encoding, modulation, etc., for a transmitter;
demodulation, decoding, decryption, etc., for a receiver, or the
like. In one example, the digital processor 630 can include a
C.times.M 640 that can control operation of the radios 620 in order
to improve the performance of the wireless device 600 as generally
described herein. The C.times.M 640 can have access to a database
644, which can store information used to control the operation of
the radios 620. As explained further below, the C.times.M 640 can
be adapted for a variety of techniques to decrease interference
between the radios. In one example, the C.times.M 640 requests a
measurement gap pattern or DRX cycle that allows an ISM radio to
communicate during periods of LTE inactivity.
For simplicity, digital processor 630 is shown in FIG. 6 as a
single processor. However, it should be appreciated that the
digital processor 630 can include any number of processors,
controllers, memories, etc. In one example, a controller/processor
650 can direct the operation of various units within the wireless
device 600. Additionally or alternatively, a memory 652 can store
program codes and data for the wireless device 600. The digital
processor 630, controller/processor 650, and memory 652 can be
implemented on one or more integrated circuits (ICs), application
specific integrated circuits (ASICs), etc. By way of specific,
non-limiting example, the digital processor 630 can be implemented
on a Mobile Station Modem (MSM) ASIC.
In an aspect, the C.times.M 640 can manage operation of respective
radios 620 utilized by wireless device 600 in order to avoid
interference and/or other performance degradation associated with
collisions between respective radios 620. C.times.M 640 may perform
one or more processes, such as those illustrated in FIG. 11. By way
of further illustration, a graph 700 in FIG. 7 represents
respective potential collisions between seven example radios in a
given decision period. In the example shown in graph 700, the seven
radios include a WLAN transmitter (Tw), an LTE transmitter (Tl), an
FM transmitter (Tf), a GSM/WCDMA transmitter (Tc/Tw), an LTE
receiver (Rl), a Bluetooth receiver (Rb), and a GPS receiver (Rg).
The four transmitters are represented by four nodes on the left
side of the graph 700. The four receivers are represented by three
nodes on the right side of the graph 700.
A potential collision between a transmitter and a receiver is
represented on the graph 700 by a branch connecting the node for
the transmitter and the node for the receiver. Accordingly, in the
example shown in the graph 700, collisions may exist between (1)
the WLAN transmitter (Tw) and the Bluetooth receiver (Rb); (2) the
LTE transmitter (Tl) and the Bluetooth receiver (Rb); (3) the WLAN
transmitter (Tw) and the LTE receiver (Rl); (4) the FM transmitter
(Tf) and the GPS receiver (Rg); (5) a WLAN transmitter (Tw), a
GSM/WCDMA transmitter (Tc/Tw), and a GPS receiver (Rg).
In one aspect, an example C.times.M 640 can operate in time in a
manner such as that shown by diagram 800 in FIG. 8. As diagram 800
illustrates, a timeline for C.times.M operation can be divided into
Decision Units (DUs), which can be any suitable uniform or
non-uniform length (e.g., 100 .mu.s) where notifications are
processed, and a response phase (e.g., 20 .mu.s) where commands are
provided to various radios 620 and/or other operations are
performed based on actions taken in the evaluation phase. In one
example, the timeline shown in the diagram 800 can have a latency
parameter defined by a worst case operation of the timeline, e.g.,
the timing of a response in the case that a notification is
obtained from a given radio immediately following termination of
the notification phase in a given DU.
As shown in FIG. 9, Long Term Evolution (LTE) in band 7 (for
frequency division duplex (FDD) uplink), band 40 (for time division
duplex (TDD) communication), and band 38 (for TDD downlink) is
adjacent to the 2.4 GHz Industrial Scientific and Medical (ISM)
band used by Bluetooth (BT) and Wireless Local Area Network (WLAN)
technologies. Frequency planning for these bands is such that there
is limited or no guard band permitting traditional filtering
solutions to avoid interference at adjacent frequencies. For
example, a 20 MHz guard band exists between ISM and band 7, but no
guard band exists between ISM and band 40.
To be compliant with appropriate standards, communication devices
operating over a particular band are to be operable over the entire
specified frequency range. For example, in order to be LTE
compliant, a mobile station/user equipment should be able to
communicate across the entirety of both band 40 (2300-2400 MHz) and
band 7 (2500-2570 MHz) as defined by the 3rd Generation Partnership
Project (3GPP). Without a sufficient guard band, devices employ
filters that overlap into other bands causing band interference.
Because band 40 filters are 100 MHz wide to cover the entire band,
the rollover from those filters crosses over into the ISM band
causing interference. Similarly, ISM devices that use the entirety
of the ISM band (e.g., from 2401 through approximately 2480 MHz)
will employ filters that rollover into the neighboring band 40 and
band 7 and may cause interference.
In-device coexistence problems can exist with respect to a UE
between resources such as, for example, LTE and ISM bands (e.g.,
for Bluetooth/WLAN). In current LTE implementations, any
interference issues to LTE are reflected in the downlink
measurements (e.g., Reference Signal Received Quality (RSRQ)
metrics, etc.) reported by a UE and/or the downlink error rate
which the eNB can use to make inter-frequency or inter-RAT handoff
decisions to, e.g., move LTE to a channel or RAT with no
coexistence issues. However, it can be appreciated that these
existing techniques will not work if, for example, the LTE uplink
is causing interference to Bluetooth/WLAN but the LTE downlink does
not see any interference from Bluetooth/WLAN. More particularly,
even if the UE autonomously moves itself to another channel on the
uplink, the eNB can in some cases handover the UE back to the
problematic channel for load balancing purposes. In any case, it
can be appreciated that existing techniques do not facilitate use
of the bandwidth of the problematic channel in the most efficient
way.
Turning now to FIG. 10, a block diagram of a system 1000 for
providing support within a wireless communication environment for
multi-radio coexistence management is illustrated. In an aspect,
the system 1000 can include one or more UEs 1010 and/or eNBs 1040,
which can engage in uplink and/or downlink communications, and/or
any other suitable communication with each other and/or any other
entities in the system 1000. In one example, the UE 1010 and/or eNB
1040 can be operable to communicate using a variety resources,
including frequency channels and sub-bands, some of which can
potentially be colliding with other radio resources (e.g., a
broadband radio such as an LTE modem). Thus, the UE 1010 can
utilize various techniques for managing coexistence between
multiple radios utilized by the UE 1010, as generally described
herein.
To mitigate at least the above shortcomings, the UE 1010 can
utilize respective features described herein and illustrated by the
system 1000 to facilitate support for multi-radio coexistence
within the UE 1010. For example, a channel monitoring module 1012,
a channel coexistence analyzer module 1014, and a power reduction
module 1016 can be provided. The channel monitoring module 1012
monitors the performance of communication channels. The channel
coexistence analyzer module 1014 analyzes potential coexistence
issues of the radios. The power reduction module 1016 may adjust
the power used by the radios to reduce potential interference from
coexistence issues. The various modules 1012-1016 may, in some
examples, be implemented as part of a coexistence manager such as
the C.times.M 640 of FIG. 6. The various modules 1012-1016 and
others may be configured to implement the embodiments discussed
herein.
Interference between a Long Term Evolution (LTE) radio access
technology and other radio access technologies, such as those
operating in the Industrial, Scientific, and Medical (ISM) band
(for example, wireless local area network (WLAN) and Bluetooth) may
result in degraded performance for the interfered with (victim)
radio. In certain scenarios, the sensitivity of the victim may not
be impacted if the aggressor's transmit power is reduced by a small
amount (called backoff). LTE transmissions in Band 7 interfering
with ISM reception and ISM transmissions interfering with LTE
receiving in Band 40 are examples of such scenarios. For other
scenarios, a certain value of a victim's received signal strength
indicator (RSSI) can coexist with the aggressor if the aggressor's
power is reduced by a few dBs. Reducing power may be achieved by
dropping a power amplifier (PA) output.
A reduced power approach may work for reducing interference between
an LTE radio and a Bluetooth/WLAN radio. Power reduction may be
adapted to the victim received signal quality. Certain factors may
determine when a reduced power approach is desired and when it is
not. Those factors may include aggressor transmit (Tx) power, error
rate observed at the victim radio, RSSI (received signal strength
indicator), throughput loss, coverage impact, etc.
Power may be reduced by an LTE transmitter to reduce interference
to other radios. A UE sends power headroom reports to an evolved
NodeB (eNB) base station on a regular basis. The eNB uses the
reduced power in scheduling the UE or a mismatch can lead to
unnecessary loss of network resources. The eNB uses the power
headroom report (PHR) and the observed UE signal-to-interference
plus noise ratio to determine whether a particular modulation
coding scheme (MCS) may be supported by the UE and what bandwidth
to allocate to the UE. One method of reducing power by x dB is for
the UE to send a power headroom report with respect to maximum
power minus x (Pmax-x) dBm and limit the transmit power to this
value. This scheme may be denoted PHR-Fake (F). This approach may
be preferred over the UE dropping its power autonomously when the
power headroom report indicates Pmax, as the latter approach may
result in the eNB assigning the UE a modulation coding scheme (MCS)
that cannot be decoded with Pmax-x dBm.
In one aspect of the present disclosure, power may be reduced by an
ISM transmitter to reduce interference to other radios. For a WLAN
radio, a rate prediction algorithm on the terminal side may reduce
power for the WLAN terminal, and determine the appropriate packet
format. For Bluetooth, a Bluetooth radio has a power control
mechanism where the remote device ensures that the received power
is suitable for decoding the used packet format. Thus, a slave
device's transmit power may be controlled by a master device and a
master device's transmit power may be controlled by a slave device.
Typically, there is a good range of receive power at the remote
device (transmit power at the terminal) where packets can be
decoded. Thus, overriding the Bluetooth power control mechanism
(i.e., setting a UE Bluetooth radio to ignore power control
messages from a remote device), and reducing transmit power on the
terminal side, is viable while staying within the desired operating
range for Bluetooth transmit power.
In another aspect of the present disclosure, a power reduction loop
is defined to control power reduction and ensure desirable
performance. Let Po be the minimum maximum power allowed (i.e., the
lowest amount of maximum power to ensure desired operation). Po may
be determined such that z % of the time the loss in throughput
should not be more than y %. Po may also be determined as the level
allowing for some g % of the current throughput seen by the user. A
loop may be run dynamically to determine what the maximum power
P(n) should be, in the range between Po and Pmax. Without the loop,
Pmax may increase to above Po, such as when the victim received
signal strength indicator is high enough that even with the
aggressor using maximum power, interference is still tolerable. The
loop may be driven by an error metric on the victim side and a
performance metric on the aggressor side. The error metric may be
.DELTA.I, the change in interference seen in the presence of an
aggressor transmission. During the loop, the max power P(n) is
increased by some .DELTA.up if the error metric improves
performance on the victim side and decreases by some .DELTA.down if
the error metric deteriorates victim performance. Thus, the loop
continually adjusts P(n) based on ongoing communication conditions.
In one configuration, the delta values are scaled based on a
difference between the target and actual performance. The scaling
may be based on victim performance and/or aggressor performance.
The scale value may also be fixed or variable depending on the
difference between target and actual performance.
A threshold, such as one based on .DELTA.I, may be set such that
the maximum loss because of coexistence interference is below some
level .xi.. If .DELTA.I exceeds the threshold a command is sent to
reduce P(n) and if .DELTA.I is below the threshold a command is
sent to increase P(n).
Power backoff/reduction may be determined in an adaptive manner
based on a victim performance target while maintaining a minimum
level of desired performance for the aggressor. The following
equations may be used to determine a level of power backoff.
Power backoff .DELTA. is equal to Pmax-current max power. If LTE
traffic is relatively inactive, that is, if the LTE duty cycle is
below a certain threshold (e.g., 5-10%), then the power backoff of
a next time point .DELTA.(n+1) remains unchanged from the previous
power backoff .DELTA.(n) and .DELTA.(n+1)=.DELTA.(n). This may also
be true if LTE is operating in a region that is not potentially
interfering with another radio access technology. If, however, LTE
is active, and the LTE duty cycle is above a certain threshold, the
power backoff value is:
.DELTA..function..DELTA..function..mu..times..function..function..mu..fun-
ction..function..function. ##EQU00001## ##EQU00001.2##
.function..alpha..function. ##EQU00001.3##
v(n) is the victim's performance metric,
v.sub.t is the victim's performance target,
a(n) is the aggressor's performance metric,
a.sub.min is the aggressor's minimum performance level, and
.mu..sub.1 and .mu..sub.2 are weights/scaling factors applied to
either the victim side (in the case of .mu..sub.1) or the aggressor
side (in the case of .mu..sub.2) to adjust those respective values
based on communication conditions and the relative desired weights
of a particular radio when determining power backoff.
The value s adjusts the power backoff calculations such that if
v(n) is greater than v.sub.t (i.e., the victim is performing above
its target level), the power backoff will be driven by the
aggressor's performance, a(n). Similarly, if a(n) is greater than
a.sub.min (i.e., the aggressor is performing above its minimum
performance level, the power backoff will be driven by the victim's
performance, v(n). For example, if LTE has a minimum rate and the
rate is being met, the power reduction is based on the Bluetooth
packet error rate. If, on the other hand, LTE is operating below
its minimum rate, the system ignores the Bluetooth packet error
rate. Thus, the parameter s allows bimodal control of the power
backoff between the aggressor and the victim, with
.alpha.=.infin..
A number of metrics may be used to determine a desired level of
performance for an aggressor radio. For example, for LTE or WLAN,
an aggressor radio may have a target minimum rate R.sub.min as the
desired metric. For Bluetooth operating in extended synchronous
connection (eSCO) mode (voice mode), a target error rate e.sub.t
may be used. For Bluetooth operating in advanced audio distribution
profile (A2DP) mode (audio mode) or LTE with delay sensitive
traffic, a target delay chosen to avoid time-outs may be used.
Also, a desired maximum backoff limit may be imposed either alone
or in conjunction with the above or other metrics. The aggressor
metric may also be any other suitable metric that captures the
impact of power backoff to the aggressor.
A number of metrics may be used to determine a desired level of
performance for a victim radio. For example, the victim metric may
be the packet error rate seen by the victim or the throughput loss
seen by the victim. For example, for Bluetooth operating in
extended synchronous connection mode, a target error rate e.sub.t
may be used. For LTE, a signal-to-interference plus noise ratio
(SINR) may be used with a target SINR being a certain offset from
the SINR without the aggressor. The offset may allow for some
degradation in the presence of the aggressor. For Bluetooth
operating in advanced audio distribution profile (A2DP) mode (audio
mode) or LTE with delay sensitive traffic, a target delay chosen to
avoid time-outs may be used. For LTE or WLAN, a target minimum rate
R.sub.min may be used as the desired metric. The victim metric may
also be any other suitable metric that captures the impact of
interference from the aggressor.
Further metrics may be considered for additional radios, should a
UE feature more than two radios. Those metrics may be considered
based on performance criteria for the additional radios, as well as
weighted scaling, and whether the additional radios are acting as
aggressors and/or victims under particular communication
conditions.
A solution is also provided to define failing criteria for power
reduction (e.g., when power reduction fails to simultaneously
satisfy minimum operating conditions of both/all radios) so that a
coexistence manager may seek a different approach, if appropriate.
For example, for the aggressor radio, if the coexistence manager
determines the terminal has a coverage issue, i.e., the current
rate (at Po) is not sufficient to support a desired level of
application quality of service, then the transmit power increases
(for example when the UE is at the edge of a cell and more transmit
power is desired). If the victim cannot handle the extra
interference from the increased transmit power, the coexistence
manager may switch away from power reduction. In the case of a
victim radio, if the aggressor is at Po and the victim cannot meet
a particular sensitivity rate or other some quality of service
measurement, then the coexistence manager may switch away from
power reduction, i.e., P(n) may be set to not go below Po. Other
criteria, such as a desired victim received signal strength
indicator can also be considered.
As shown in FIG. 11 a UE may determine a performance metric of an
aggressor radio and a performance metric of a victim radio as shown
in block 1102. A UE may dynamically set a maximum transmit power of
the aggressor radio based on at least one of the performance metric
of the victim radio and the performance metric of the aggressor
radio in order to meet target performance criteria for the victim
radio and aggressor radio as shown in block 1104.
A UE may comprise means for determining a performance metric of an
aggressor radio and a performance metric of a victim radio. In one
aspect, the aforementioned means may be the coexistence manager
640, the memory 272, and/or the processor 270 configured to perform
the functions recited by the aforementioned means. The UE may also
comprise means for dynamically setting a maximum transmit power of
the aggressor radio based on at least one of the performance metric
of the victim radio and the performance metric of the aggressor
radio in order to meet target performance criteria for the victim
radio and aggressor radio. In one aspect, the aforementioned means
may be power reduction module 1016, the coexistence manager 640,
the memory 272, and/or the processor 270 configured to perform the
functions recited by the aforementioned means. In another aspect,
the aforementioned means may be a module or any apparatus
configured to perform the functions recited by the aforementioned
means.
FIG. 12 shows a design of an apparatus 1300 for a UE. The apparatus
1200 includes a module 1202 to determine a performance metric of an
aggressor radio and a performance metric of a victim radio. The
apparatus also includes a module to dynamically set a maximum
transmit power of the aggressor radio based on at least one of the
performance metric of the victim radio and the performance metric
of the aggressor radio in order to meet target performance criteria
for the victim radio and aggressor radio. The modules in FIG. 12
may be processors, electronics devices, hardware devices,
electronics components, logical circuits, memories, software codes,
firmware codes, etc., or any combination thereof.
The examples above describe aspects implemented in an LTE system.
However, the scope of the disclosure is not so limited. Various
aspects may be adapted for use with other communication systems,
such as those that employ any of a variety of communication
protocols including, but not limited to, CDMA systems, TDMA
systems, FDMA systems, and OFDMA systems.
It is understood that the specific order or hierarchy of steps in
the processes disclosed is an example of exemplary approaches.
Based upon design preferences, it is understood that the specific
order or hierarchy of steps in the processes may be rearranged
while remaining within the scope of the present disclosure. The
accompanying method claims present elements of the various steps in
a sample order, and are not meant to be limited to the specific
order or hierarchy presented.
Those of skill in the art would understand that information and
signals may be represented using any of a variety of different
technologies and techniques. For example, data, instructions,
commands, information, signals, bits, symbols, and chips that may
be referenced throughout the above description may be represented
by voltages, currents, electromagnetic waves, magnetic fields or
particles, optical fields or particles, or any combination
thereof.
Those of skill would further appreciate that the various
illustrative logical blocks, modules, circuits, and algorithm steps
described in connection with the aspects disclosed herein may be
implemented as electronic hardware, computer software, or
combinations of both. To clearly illustrate this interchangeability
of hardware and software, various illustrative components, blocks,
modules, circuits, and steps have been described above generally in
terms of their functionality. Whether such functionality is
implemented as hardware or software depends upon the particular
application and design constraints imposed on the overall system.
Skilled artisans may implement the described functionality in
varying ways for each particular application, but such
implementation decisions should not be interpreted as causing a
departure from the scope of the present disclosure.
The various illustrative logical blocks, modules, and circuits
described in connection with the aspects disclosed herein may be
implemented or performed with a general purpose processor, a
digital signal processor (DSP), an application specific integrated
circuit (ASIC), a field programmable gate array (FPGA) or other
programmable logic device, discrete gate or transistor logic,
discrete hardware components, or any combination thereof designed
to perform the functions described herein. A general purpose
processor may be a microprocessor, but in the alternative, the
processor may be any conventional processor, controller,
microcontroller, or state machine. A processor may also be
implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
The steps of a method or algorithm described in connection with the
aspects disclosed herein may be embodied directly in hardware, in a
software module executed by a processor, or in a combination of the
two. A software module may reside in RAM memory, flash memory, ROM
memory, EPROM memory, EEPROM memory, registers, hard disk, a
removable disk, a CD-ROM, or any other form of storage medium known
in the art. An exemplary storage medium is coupled to the processor
such the processor can read information from, and write information
to, the storage medium. In the alternative, the storage medium may
be integral to the processor. The processor and the storage medium
may reside in an ASIC. The ASIC may reside in a user terminal. In
the alternative, the processor and the storage medium may reside as
discrete components in a user terminal.
The previous description of the disclosed aspects is provided to
enable any person skilled in the art to make or use the present
disclosure. Various modifications to these aspects will be readily
apparent to those skilled in the art, and the generic principles
defined herein may be applied to other aspects without departing
from the spirit or scope of the disclosure. Thus, the present
disclosure is not intended to be limited to the aspects shown
herein but is to be accorded the widest scope consistent with the
principles and novel features disclosed herein.
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